Antique rail parts sold as scrap metal by a recidivist fraudster for $600 will cost a Dunedin heritage organisation more than $50,000 to replace, a court has heard.

Lloyd Denise Odell (31) appeared in the Dunedin District Court yesterday after pleading guilty to theft.

Judge Michael Crosbie jailed him for 15 months after delving into the defendant's past and attempting to find out what "made him tick".

"Are you misunderstood and fallen through the cracks or cunning, manipulative and take advantage of other people?" he asked.

While Odell tried to convince him he had turned his life around, the judge settled on the latter proposition.

The defendant joined the Otago Railway and Locomotive Society in February last year and in doing so received a key that gave him access to the St Kilda workshop sheds of Ocean Beach Railway.

"There are people and communities that are quite passionate about their heritage and Otago is one," Judge Crosbie said.

"You're standing in a heritage building [the refurbished courthouse], you're standing in a heritage dock; and members of this organisation are passionate about the heritage of rail."

But Odell did not share their love of history. Instead, he began stealing antique steam engine and carriage parts.

In August, he took the items - including a handrail, lights and numerous brass and copper fittings - to a scrap metal dealer, for which he received $592.

In his victim impact statement to the court, the chairman of the society said the parts would cost at least $50,000 to replace.

The group, set up in 1961, had collected 11 locomotive carriages, the court heard, and some pieces dated back to the 1870s.

Dunedin was one of the few places in the world where a complete Victorian-era train could be assembled, the chairman said.

Knowing the theft came from someone in whom they had placed trust was "heart-breaking".

The organisation believed Odell had specifically targeted them and it had been his intention from the moment he was given access to the workshop.

But counsel Andrew Dawson said that was denied.

"He has made it very clear this wasn't a great plan instituted for some time ... he genuinely wanted to assist," he said.

"He simply didn't turn his mind to the rare nature of the things he was taking."

After perusing psychological reports compiled about Odell in recent years, Judge Crosbie concurred with the documents that the man's risk of reoffending was high.

"You just aren't getting the message," he said.

"You have the ability to work, to do something decent with your life but you take the easy route. It's lazy and at the age of 31 with a lot of life ahead of you, you need to start taking a mature and hard-working approach to life."